[evlatests] Temperature control in vertex room

[Vivek Dhawan]

During evaluation of the new L352 round-trip phase
meters, it was found that EA17 had large temperature
swings (~3 C) on a timescale of 20-30 min. A survey
was done of all EVLA antennas with P301 (LO rack)
temperature sensors, and many antennas were found
out of spec.  A list is below, and a plot has been
circulated to the powers that be in charge of HVAC.

  ea01 - good
  ea11 - worst, day and night - short spikes ~4deg C.
  ea17 - bad, except just before dawn
  ea19 - variable, bad at midday
  ea21 - spikes, ~2 C.
  ea24 - slow variations, plus 6deg diurnal swing.
  ea25 - good mostly. spikes on some monitor point.
  ea26 - could be better.

11 has the worst phase rms, and the worst temp habits.
1 is the converse. Phase stability tests (early February,
using antennas 17 and 19 according to the current plan)
require temperature stability at least on those antennas.